- Would you hold a person back by virtue of time-served alone even if it's evident they are proficient enough to move forward?

No.

- Do you consider prior martial arts experience when someone joins your club when placing them in a class (for instance, beginner, intermediate or advanced), or is that irrelevant? Why or why not?

Yes and No. Everyone starts at the beginning, but you evaluate a transfer student and move them up according to ability. And despite your notion that someone with prior experience will have the skills in place to transition to a new style, I find that isn't so. Good martial artists can do it. Bad ones are bad in any art. And then there are those that simply can't let go of prior training and won't make progress in a new school.

- For those in the area of tae kwon do, how would you handle a situation where someone with a black belt in tae kwon do, but from a different organization joins your club? For instance a black belt from ITF starting WTF, or a black belt from WTF starting Song Moo Kwan, or vice versa, etc.? Do they start at white belt, do they start as a black belt, do they start somewhere in between? What is the rationale for your response?

Not TKD, but my teachers were and transitioned to Goju. No matter the style, a BB transitioning is evaluated on skill. Don't cut the mustard and you are relegated to the appropriate (underlevel) training class.

- Is "time-served" set in stone, or is the fitness level, prior athletic experience, natural ability, rate of learning, etc. an important thing to consider?

'Time served' doesn't get anyone a pass on ability. Natural ability will get one only so far, and training, good or bad, will show. Anyone claiming a BB in another art isn't really considered as 'all that'. But when claiming 'time served', stating 'I've trained 20 years in XX', that is a different matter. That person is expected to have figured out a lot more and is going to be evaluated more critically. (I just love all the weekend warriors with shodan/nidan that claim 10-20 years of training, show up, and can't deflect a punch.)

-The situation I am specifically referring to is an individual with 14 years of experience in Tae Kwon Do recently took and passed their belt promotion from black stripe to double black stripe (the belt before black belt at my club) two months after their last belt test. This individual has a black belt in Song Moo Kwan Tae Kwon Do, but was forced to switch styles several years ago because it isn't taught in very many locations. The club they originally started before joining my club asked them to start at purple belt (the half way point), which they did. It has been three years since. They passed their belt test and no-one questions their ability, yet the manager of another location of the same club (there are three locations of the club I belong to) is really upset they were permitted to take their belt promotion test after only two months.

I'm not sure where I stand on the issue and I wanted to gauge the general consensus in the martial arts community.

Hung up on petty rank. One stripe, two stripes. How about a gold star to go with that? Only thing that matters is your training, and whether or not the school you are training in is actually teaching you something of value and not holding you back.